C8051F504-IQ Silicon Laboratories Inc, C8051F504-IQ Datasheet - Page 58

• Manufacturer Part Number: C8051F504-IQ
• Description: IC 8051 MCU 32K FLASH 48-QFP
• Manufacturer: Silicon Laboratories Inc
• Series: C8051F50xr

Specifications of C8051F504-IQ

• Program Memory Type: FLASH
• Program Memory Size: 32KB (32K x 8)
• Package / Case: 48-QFP
• Mfg Application Notes: LIN Bootloader AppNote
• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 50MHz
• Connectivity: EBI/EMI, SMBus (2-Wire/I²C), CAN, LIN, SPI, UART/USART
• Peripherals: POR, PWM, Temp Sensor, WDT
• Number Of I /o: 40
• Ram Size: 4.25K x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 5.25 V
• Data Converters: A/D 32x12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 125°C
• Processor Series: C8051F5x
• Core: 8051
• Data Bus Width: 8 bit
• Data Ram Size: 4.25 KB
• Interface Type: I2C/SPI/UART
• Maximum Clock Frequency: 50 MHz
• Number Of Programmable I/os: 40
• Number Of Timers: 4
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: PK51, CA51, A51, ULINK2
• Development Tools By Supplier: C8051F500DK
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 32-ch x 12-bit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: 336-1527 - KIT DEV FOR C8051F50X
• Eeprom Size: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 336-1518

C8051F50x/F51x
6.3. Selectable Gain
ADC0 on the C8051F50x/F51x family of devices implements a selectable gain adjustment option. By writ-
ing a value to the gain adjust address range, the user can select gain values between 0 and 1.016.
For example, three analog sources to be measured have full-scale outputs of 5.0 V, 4.0 V, and 3.0 V,
respectively. Each ADC measurement would ideally use the full dynamic range of the ADC with an internal
voltage reference of 1.5 V or 2.2 V (set to 2.2 V for this example). When selecting the first source (5.0 V
full-scale), a gain value of 0.44 (5 V full scale x 0.44 = 2.2 V full scale) provides a full-scale signal of 2.2 V
when the input signal is 5.0 V. Likewise, a gain value of 0.55 (4 V full scale x 0.55 = 2.2 V full scale) for the
second source and 0.73 (3 V full scale x 0.73 = 2.2 V full scale) for the third source provide full-scale ADC0
measurements when the input signal is full-scale.
Additionally, some sensors or other input sources have small part-to-part variations that must be
accounted for to achieve accurate results. In this case, the programmable gain value could be used as a
calibration value to eliminate these part-to-part variations.
6.3.1. Calculating the Gain Value
The ADC0 selectable gain feature is controlled by 13 bits in three registers. ADC0GNH contains the 8
upper bits of the gain value and ADC0GNL contains the 4 lower bits of the gain value. The final GAINADD
bit (ADC0GNA.0) controls an optional extra 1/64 (0.016) of gain that can be added in addition to the
ADC0GNH and ADC0GNL gain. The ADC0GNA.0 bit is set to 1 after a power-on reset.
The equivalent gain for the ADC0GNH, ADC0GNL and ADC0GNA registers is as follows:
Where:
GAIN is the 12-bit word of ADC0GNH[7:0] and ADC0GNL[7:4]
GAINADD is the value of the GAINADD bit (ADC0GNA.0)
gain is the equivalent gain value from 0 to 1.016
58
Equation 6.2. Equivalent Gain from the ADC0GNH and ADC0GNL Registers
P x . x
Figure 6.5. ADC0 Equivalent Input Circuit
gain
R C
M U X S e l e c t
I n p u t
=


= R
GAIN
-------------- -
4096
M U X


+
Rev. 1.2
* C
GAINADD
R
M U X
S A M P L E



----- -
64
1


C
S A M P L E